I just got this off of Bugtraq today. I thought that some of you might find it useful.

Unchecked Buffer in File Decompression Functions Could Lead to Code Execution (Q329048)

Originally posted: October 02, 2002


Who should read this bulletin: Customers using Microsoft® Windows® 98 with Plus! Pack, Windows Me, or Windows XP

Impact of vulnerability: Two vulnerabilities, the most serious of which could run code of attacker's choice

Maximum Severity Rating: Moderate

Recommendation: Consider applying the patch to affected systems

Affected Software:
- Microsoft Windows 98 with Plus! Pack
- Microsoft Windows Me
- Microsoft Windows XP

Technical description:

Zipped files (files having a .zip extension) provide a means to store information in a way that uses less space on a hard disk. This is accomplished by compressing the files that are put into in the zipped file. On Windows 98 with Plus! Pack, Windows Me and Windows XP, the Compressed Folders feature allows zipped files to be treated as folders. The Compressed Folders feature can be used to create, add files to, and extract files from zipped files.

Two vulnerabilities exist in the Compressed Folders function:
- An unchecked buffer exists in the programs that handles the decompressing of files from a zipped file. A security vulnerability results because attempts to open a file with a specially malformed filename contained in a zipped file could possibly result in Windows Explorer failing, or in code of the attacker's choice being run.
- The decompression function could place a file in a directory that was not the same as, or a child of, the target directory specified by the user as where the decompressed zip files should be placed. This could allow an attacker to put a file in a known location on the users system, such as placing a program in a startup directory

Mitigating factors:
- The vulnerabilities could not be exploited without user intervention. The attacker would need to entice the user to receive, store, and open the zipped file provided by the attacker.
- The vulnerabilities could not be exploited remotely. An attacker would need to lure a user into receiving the zipped file onto the user's machine. Best practices suggest users not accept e-mail attachments from people who are not trusted, and not to download files from untrusted Internet sites.
- On Windows 98 and Windows Me, the Compressed Folders feature is not installed by default. Users who had not installed this feature would not be vulnerable.

Vulnerability identifiers:
- Unchecked Buffer in Zipped File Handling: CAN-2002-0370
- Incorrect Target Path for Zipped File Decompression: CAN-2002-1139